Melanoma skin cancer can be fatal unless caught early, but most skin lesions are harmless. Dermoscopy with training can help with diagnosis. This blog is not a substitute for a medical opinion-if you are worried about a changing or funny looking mole or spot, get it checked by a doctor with suitable skills.

Deceitful warty lesion

An older white male presented with a slowly but steadily growing solitary lesion on the lower abdomen. Present about 2 or 3 years, dimensions about 2.5cm long and almost 1cm thick. Definitely a stuck on appearance and some keratin. These features point to a seborrhoiec keratosis or wart.

A traumatised seborrhoiec keratosis was tentatively diagnosed and the lesion shaved off for histology in one piece using a dermablade.

This is the dermoscopy.

It is hard to describe this. The first word that comes to mind is ‘chaos’ or multicomponent. Parts of it definitely look papillomatous or warty.

Remember the rule my mentor Dr Catriona Henderson gave me: when evaluating suspicious lesions look for Symmetry, count the COlours, count the Patterns, and look round the Edge (SCOPE). We see no symmetry here, colours grey, brown, red, yellow and white, patterns at least 4, and the edge is somewhat irregular.

Histology was of a thick melanoma.

I have shown these pictures to a lot of people, some very experienced. Most of them initially suspected a traumatised seborrhoiec keratosis, as did I, but something was definitely not right. Verrucous melanomas are uncommon but very deceitful.

never forget our most basic algorithm.

1) could this be a melanocytic lesion?

2) if so, can I confidently say it is benign or could it be a melanoma?

This particular lesion does not have any reticular network or globules, but that does not rule out melanoma since amorphous or multi-pattern can also mean melanocytic. The key learning point is that you cannot safely and on positive grounds ascribe this lesion to any category of benign lesion. This leads us to the inevitable conclusion that it should be urgently excised for histology.

Incidentally, I have just shown this lesion-plain view first, then dermoscopy- to my current learning group. A majority thought it was probably a seb k on the plain view, but on dermoscopy immediately felt more suspicious. Dermoscopy reveals more information which if properly interpreted can acquit or condemn a doubtful lesion.

Always try to make a positive diagnosis of benignity, or if you can’t then do something about it.